If you watch/play X backwards, it's about Y ...

If you play The Last Of Us backwards it's about a father and daughter-like pair trying to get from the wild, full of infected, to the quarantine zone.

If you play Amnesia backwards, it's about a god who descends from above, resurrects a sadist, then travels through the sadist's castle chasing monsters, regains his memory, and joins the sadist in torturing people.

If you play Medieval total war 2 is about a huge empire that looses it's lands until it becomes a small and poor country.